The instant invention relates to a yarn splicing device for the knot-free piecing of yarns. The device includes a yarn splicing chamber and a small pipe through which fluid flows which is installed at a distance from the yarn splicing chamber to receive a yarn end to be prepared for the splicing process. The invention also includes a process for the yarn end preparation in such a yarn splicing device.
In order to achieve good quality in the piecing joint, the piecing of yarn ends by splicing requires that the preparation of the yarn ends be carried out with care. The yarn end must be free of twist over a certain length so that it can be pieced properly in the spinning device to a second yarn end which is also essentially free of twist.
It is known that the yarn ends are prepared in devices in which said yarn ends are subjected to a stream of fluid which seizes the yarn at a right angle to the longitudinal axes of the yarns by means of pressure or suction force thus produced and which swirls them so that the yarn ends are untwisted. The preparation of only one yarn end in the known device shall be described below.
In the known device, the stream of fluid enters a small pipe into which it pulls or pushes the yarn end at an angle to the longitudinal axis and the yarn end is untwisted by the turbulent flow thus produced against its twist. The fibers constituting the yarn end are freed by this flow and are spread out. Conventional ring spun yarns can be spliced successfully in this manner.
It is more difficult to splice multiple yarns or threads consisting of two or more individual strands twisted around each other, where the twist of the individual strands goes in the opposite direction to the twist of the yarn constituted by the individual strands twisted around each other. German Patent No. 3,417,367 deals with such an improvement. According to this known design, a stream of fluid is brought into each nozzle pipe at an angle to the longitudinal axis of the nozzle pipe, with the stream of fluid striking an impact plate installed within the nozzle pipe. When the stream of fluid strikes the impact plate, turbulent flows are produced in which the yarn end portion executes non-swirling movements, i.e., pitching movements and oscillations which causes the twist of the individual strands to be undone.
Another known device (German Patent No. DE 3,151,270 A1) proposes a more intensive mechanical and pneumatic stressing of the yarn ends for the same purpose, that is, to open the yarn ends into individual fibers, to clean the fibers and to spread them out. This is effected in that the gas under pressure, streaming at an angle to the longitudinal direction of the individual fibers, causes the yarn ends to oscillate while at the same time battering, tearing and pulling mechanical and pneumatic forces act upon the yarn end. This process is relatively expensive. It, furthermore, involves the danger that such intensive, violent opening of the yarn ends causes the individual fibers to be damaged so that they are no longer suitable for a good splicing joint.
The yarns produced by new spinning methods pose a special problem for splicing. This applies, in particular, to yarns produced by the open-end rotor spinning process, in the fiber wind-around spinning process or in similar new spinning processes. This type of yarn manufacture does not produce uniform twist in the yarn. Furthermore, these yarns often have individual fibers wound around the yarn (so-called belly bands) which are very difficult to undo. The splicing methods used until now have proven to be of little use for this, and this is the reason why the splicing of such yarns still presents a problem today.